TUBULARIAE 



95 



Fig. 151 Clava lep- 

 tostyla (Nutting). 



Key to the genera of Clavidae here described : 



a x Colony not branching ; polyps rising from a filiform hydrorhiza. 



6j Sporosacs borne on hydranths 1. CLAVA 



& 2 Sporosacs spring from hydrorhiza 2. RHIZOGETON 



a 2 Colony branching 3. CORDYLOPHORA 



1. CLAVA Gmelin. Simple unbranched hydranths rise from a fili- 

 form hydrorhiza; this is protected by a perisarc which extends a short 

 distance up the hydranth; sporosacs in clusters at 



the base of the tentacles: 5 species. 



C. leptostyla Agassiz (Fig. 151). Hydranths 

 reddish in color, about 2 cm. long, with about 20 

 tentacles; male sporosacs pink, female purple: 

 common in shallow water on fucus, piles, etc., from 

 Long Island Sound to Labrador; California. 



2. RHIZOGETON Agassiz. Similar to Clava, 

 except that the sporosacs arise from the hydro- 

 rhiza on short stalks : 1 species. 



R. fusiformis Ag. Hydranth about 8 mm. 

 high, with 12 tentacles; sporosacs shorter and 

 invested with the perisarc: in rock pools in Massachusetts Bay. 



3. CORDYLOPHORA* Allman. Colony profusely branching, the hy- 

 dranths with scattered filiform tentacles being at the ends of the 



branches ; sporosacs ovate, 



L / ffc springingfromthe 



branches; with a definite 

 perisarc: 2 species. 



C. lacustris All. (Fig. 

 152). Colony about 20 to 

 30 mm. high ; hydranth with 

 10 to 20 tentacles : on rocks, 

 eel grass, etc., in brackish 

 and fresh water, being one 

 of the very few fresh-water 

 coelenterates ; Rhode Island ; 

 Massachusetts ; Illinois ; 

 sometimes rather common; 

 Europe. 



Fig. 152 



Fig. 153 



Fig. 152 Cordylophora lacustris (Siissw. F. 



Deut.). 1, hydranth; 2, hydrocaulus ; 3, 



hydrorhiza. Fig. 153 Syncoryne 



mirabilis (Agassiz). 



FAMILY 2. COEYNIDAE. 



Trophosome: colony branched or not, with long, slender hydro- 

 eaulus and cylindrical hydranths bearing numerous knobbed tentacles 



* See "Hydroids in the Illinois River," by F. Smith, Biol. Bull., Vol. IS, p. 67, 1910. 



